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From Peter Wolf <opus...@gmail.com>
Subject Re: Confirming a Bug
Date Fri, 23 Mar 2012 01:01:46 GMT
Hello again Lars and Lars,

Here is some additional information that may help you track this down.

I think this behavior has something to do with my VPN.  My servers are 
on the Amazon Cloud and I normally run my client on my laptop via a VPN 
(Tunnelblick: OS X 10.7.3; Tunnelblick 3.2.3 (build 2891.2932)).  This 
is where I see the buggy behavior I describe.

However, when my Client is running on an EC2 machine, then I get 
different behavior.  I can not prove that it is always correct, but in 
at least one case my current code does not work on my laptop, but gets 
the correct number of results on an EC2 machine.  Note that my scans are 
also much faster on the EC2 machine.

I will do more tests to see if I can localize it further.

Hope this helps
Thank you again
Peter


On 3/19/12 2:24 PM, Peter Wolf wrote:
> Hello Lars and Lars,
>
> Thank you for you help and attention.
>
> I wrote a standalone test that exhibits the bug.
>
> http://dl.dropbox.com/u/68001072/HBaseScanCacheBug.java
>
> Here is the output.  It shows how the number of results and key value 
> pairs varies as caching in changed, and families are included.  It 
> shows the bug starting with 3 families and 5000 caching.  It also 
> shows a new bug, where the query always fails with an IOException with 
> 4 families.
>
> CacheSize FamilyCount ResultCount KeyValueCount
> 1000 1 10000 10
> 5000 1 10000 10
> 10000 1 10000 10
> 1000 2 10000 20
> 5000 2 10000 20
> 10000 2 10000 20
> 1000 3 10000 30
> 5000 3 5000 30
> 10000 3 0 -1
> Exception in thread "main" java.lang.RuntimeException: 
> org.apache.hadoop.hbase.client.RetriesExhaustedException: Trying to 
> contact region server domu-12-31-39-05-6d-02.compute-1.internal:60020 
> for region bug,,1332174647830.ef906b7bd8eea8482c84edd906df24fd., row 
> '\x00\x00\x00{\x00\x00\x00\x00\x00\x00\x00\x00', but failed after 10 
> attempts.
> Exceptions:
> java.io.IOException: java.io.IOException: Call to ... failed on local 
> exception: java.io.IOException: Unexpected exception receiving call 
> responses
>     at 
> org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.getRegionServerWithRetries(HConnectionManager.java:1231)
>     at 
> org.apache.hadoop.hbase.client.HTable$ClientScanner.next(HTable.java:1170)
>     at 
> org.apache.hadoop.hbase.client.HTable$ClientScanner$1.hasNext(HTable.java:1275)
>     ... 7 more
>
>
> Here is the main().  Note that createTable() and createData() are 
> commented out.  Uncomment these to populate the test table.
>
>     public static void main(String[] args) {
>
>         try {
>             //createTable("bug");
>
>             HBaseScanCacheBug bug = new HBaseScanCacheBug("bug");
>             int id = 123;
>
>             //bug.createData(id);
>
>             System.out.println("CacheSize FamilyCount ResultCount 
> KeyValueCount");
>             for (int familyCount = 1; familyCount < 5; familyCount++) {
>                 bug.scan(id, 1000, familyCount);
>                 bug.scan(id, 5000, familyCount);
>                 bug.scan(id, 10000, familyCount);
>             }
>
>         } catch (IOException e) {
>             throw new Error(e);
>         }
>
>     }
>
>     private static Configuration getConfiguration() {
>         Configuration conf = HBaseConfiguration.create();
>         conf.set("hbase.zookeeper.quorum", "Put Your Server Here");
>         conf.setInt("hbase.client.prefetch.limit", 100);
>         return conf;
>     }
>
>
>
> On 3/19/12 5:58 AM, Lars George wrote:
>> Hi Peter,
>>
>> Lars #1 here again :)
>>
>> That is fine, the caching is done transparently for you. But what I 
>> also suggest is counting the number of KeyValues you get back, just 
>> to confirm. In other words, iterate over the result and check how 
>> many actual KVs you get back. The reason I am asking is that for 
>> example scanner batching will change the behavior, you will get a 
>> Result instance per batch, not per row.
>>
>> Thanks for digging in!
>>
>> Lars
>>
>> On Mar 19, 2012, at 12:40 AM, Peter Wolf wrote:
>>
>>> Excellent!   Thank you very much (other) Lars.
>>>
>>> I have only tested this one one dataset, and only on a few values of 
>>> caching.  I certainly get different results with 10,000 5,000 and 
>>> 1,000 caching.  1,000 gives me the same results as default.  I also 
>>> get different results when I add families to the Scan.
>>>
>>> I seem to be surpassing some maximum buffer size.  The number of 
>>> results is always the correct value - some multiple of the cache 
>>> size.  For example, the correct value was 24,452, but when caching 
>>> was set to 10,000, I got 4,452 results.  When I then removed a 
>>> family from the scan, I got 14,452 results.
>>>
>>> I'll try to write a standalone program to reproduce this.  I'll get 
>>> back to you soon.
>>>
>>> P
>>>
>>> P.S.  I just want to check.  The following code counts the number of 
>>> results.  I don't need to do anything to "get the next cache" or 
>>> something do I?
>>>
>>>          Iterator<Result>    it = scanner.iterator();
>>>          while (it.hasNext()) {
>>>              Result result = it.next();
>>>              ...
>>>          }
>>>
>>>
>>>
>>>
>>> On 3/18/12 5:51 PM, lars hofhansl wrote:
>>>> Hi Peter,
>>>>
>>>> (this is the other Lars)
>>>>
>>>>
>>>> Does this depend on your dataset at all? Does not it also happen 
>>>> for smaller value of scanner caching?
>>>>
>>>>
>>>> Any chance that you can reproduce this in a unittest and file a jira?
>>>> If you do (specifically the test), I'll promise I'll look at it 
>>>> this week :)
>>>>
>>>>
>>>> -- Lars (H)
>>>>
>>>>
>>>>
>>>> ________________________________
>>>>   From: Peter Wolf<opus111@gmail.com>
>>>> To: user@hbase.apache.org
>>>> Sent: Sunday, March 18, 2012 7:13 AM
>>>> Subject: Re: Confirming a Bug
>>>>
>>>> Hi Lars,
>>>>
>>>> I don't think so...  My behavior is definitely tied to the amount of
>>>> data in each Result.  There definitely seems to be some sort of
>>>> threshold.  Changing the caching amount produces a completely 
>>>> repeatable
>>>> behavior.  10,000, 5,000, and 1000 each produce different repeatable
>>>> results, and changing the families added as produces different 
>>>> reliable
>>>> results. There is no "sometimes" or "occasional", and if there was a
>>>> Major Compaction, it wouldn't happen that often.
>>>>
>>>> https://issues.apache.org/jira/browse/HBASE-5121
>>>> https://issues.apache.org/jira/browse/HBASE-2856
>>>>
>>>> Note that with all my families added each result is a few 1000 bytes
>>>> big.  Is that unusually large?
>>>>
>>>> Thanks
>>>> P
>>>>
>>>>
>>>>
>>>> On 3/18/12 5:28 AM, Lars George wrote:
>>>>> Hi Peter,
>>>>>
>>>>> Could you be hitting HBASE-5121? Or even HBASE-2856?
>>>>>
>>>>> Lars
>>>>>
>>>>> On Mar 17, 2012, at 20:46, Peter Wolf<opus111@gmail.com>    wrote:
>>>>>
>>>>>> Hello,
>>>>>>
>>>>>> A couple of days ago, I asked about strange behavior in my 
>>>>>> "Scan.addFamiliy reduces results" thread.
>>>>>>
>>>>>> I want to confirm that I did find a bug, and if so, how to submit

>>>>>> a bug report.
>>>>>>
>>>>>> The basic strangeness is that changing the amount of caching, 
>>>>>> changes the number of results.  In the original thread, this was

>>>>>> confused by the fact that adding different families also changed

>>>>>> the number of results.  We thought it was a filtering problem.
>>>>>>
>>>>>> However, changing nothing but the setCaching() value changes the

>>>>>> number of results.  Furthermore, the result difference is a 
>>>>>> multiple of the setCaching() value.
>>>>>>
>>>>>> Here is the pseudo code:
>>>>>>
>>>>>>           Scan scan = new Scan(...);
>>>>>>           scan.addFamily(...);
>>>>>>           Filter filter = ...
>>>>>>           scan.setFilter(filter);
>>>>>>
>>>>>> -->        scan.setCaching(10000);<--
>>>>>>
>>>>>>           scanner = hTable.getScanner(scan);
>>>>>>           Iterator<Result>    it = scanner.iterator();
>>>>>>           while (it.hasNext()) {
>>>>>>               Result result = it.next();
>>>>>>               ...
>>>>>>           }
>>>>>>
>>>>>>
>>>>>> Thank you
>>>>>> Peter
>


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